We have some .mir files which we can open successfully in TVPaint Pro 8.5.4.

We know absolutely nothing about TVPaint, and are having trouble exporting the .mir file as a .psd file retaining layers. We can get it to export as a single layer file, but not with all layers retained in the .psd.

Is this possible? If so, would someone be kind enough to let us know the process? Thanks!

in: file > export project to.. (this opens the export footage panel) you should select the 'project layers' Tab
here you only have the PSD format so you don't need to select it
so if you want to save an animation you now only have to check te sequence box as a sequence of psd's
else check 'single image' and it will save your layered image as a single PSD.